Ali - may Allah be pleased with him can help no one after his death
Question :
Does Ali, may Allah be pleased with him, help anyone in times of calamities?
Answer:
Ali, may Allah be pleased with him, was killed without being aware of his assassin's scheme, nor was he able to protect himself from it. How then could it be alleged that he can ward off calamities from others after his death, when he could not ward it off from himself when he was alive? He who believes that Ali or any dead person can extend a benefit to others, or help them obtain it, or ward off evil from them is Mushrik, because these things are restricted to Allah, Glorious is He. Therefore, whoever believes that a creature can do that and he seeks his help, then he takes such one for a god. Allah, the Exalted, says:" And if Allah inflicts harm on you, there is none who can remove it except He. And if He intends to do good for you, there is none to repel His Bounty. He makes it reach whomsoever of His slaves he wills. He is the Forgiving, the Merciful".
Source:
Fatawa Islamiyah, Vol. 1 Page 28